I'm going to share my experience on moving the Users folder on Windows 10 build 10240, coming from Windows 8.1.
Prior to upgrading, my machine was running Windows 8.1 Pro with the users directory in its default location (C:\Users). I backed up all my important files to a network drive, then proceeded with the usual upgrade process using an ISO created from the leaked 10240 ESD files. I chose the first option (keep my Windows settings, apps and files). The upgrade went smoothly.
After the first boot, I decided to start from a clean installation of Windows 10 by using the Reset feature (Settings > Update & Security > Recovery > Reset this PC). No problems yet.
Once the Reset has completed, I followed the tutorial, pressing Ctrl+Shift+F3 on the "Select language" screen. This successfully rebooted me to Audit mode. I followed the rest of the steps (create answer file, sysprep, etc), making one small change to the answer file included in the tutorial:
wim:E:\sources\install.wim#Windows 10 Pro
After sysprepping and my PC rebooting to the "Select language" screen again, I set up my PC as usual, using my Microsoft account to set up my user account. However, after I booting into the Desktop, I could not open the Store. I was unable to figure out why this happened, and I was not able to find a fix.
wim:E:\sources\install.wim#Windows 10 Pro Insider Preview
I decided to do a true clean install instead by booting from USB and wiping the entire C: drive before installing Windows 10. Once the installation was complete, I followed the tutorial again (Audit mode, sysprep, etc) however, this time I opted to keep my PC disconnected from the internet (not sure if this is relevant). I also opted to create a local account instead of using my Microsoft account in setting up my PC (not sure if this is relevant also). Once I was able to boot into the Desktop that's when I connected to the internet and changed my local account to a Microsoft account. I checked the store and it was working.
Anyway, I have been using this configuration for about a week now, with no major problems so far. Majority of the Store apps and desktop apps I use function properly even when the Users directory is in a different drive. The only app I had a minor issue with was AMIDuOS, where it refused to create a virtual machine when the user folder is in D. I was able to easily fix this by creating a directory junction from C:\Users to D:\Users.
Hopefully this helps out someone. And thanks Kari for a great tutorial.